So this is just a question out of curiosity, hopefully some one can clarify for me as different shop assistants have told me different things.

(and I also hope you can understand the question, as my conversing skills aren't too sharp )

So basically there is a temperature rating on sleeping bags, I want to know if your planning a trip and you can expect -9(ish) ° temps do you need to then hunt for the biggest baddest down bag that exceeds that temp rating? Or could you go for a bag thats rated to say -5° and be relatively comfy?

I understand that every person is different in terms of sleeping warmth due to metabolism and all that. But Im talking average oke, doing some average winter nights in Boven

I take it you will be in a tent when using this bag. 2 people in a tent normally keep the temperature in the tent well above ambient temperature. I cannot see it getting down to -5 inside a tent in Boven, but admittedly I have never camped at Boven in the winter. I have used a -8 rated bag over the last few years in and out of tents and I used it with a fleece inner when it was -20 outside and about -15 inside the tent and I would be lying if I said I was comfortable. That said it was more than sufficient for a mid winter traverse of the Hex River range where it got fairly cold.

I've got a fleece inner and it works kinda well, only thing I don't like is that you can get tangled up in the thing especially if you tie it to the little tabs provided. If you're gonna be facing temps like that on a regular basis go for a down bag. I got a First Ascent Fusion 900 rated -15 and pure bliss

some more thoughts:
temperature ratings are not consistent between manufacturers. some thumbsuck i'm sure; whereas for others the rating is either "comfort" or "extreme" (survival) temperature. a -9 "extreme" bag is probably around -3 "comfort" (?) in saffa a -9 comfort bag should cover just about everyting and you can add temp with tent / shelter & warm clothing. and a down bag is just the best! first ascent ice braker or similar.
maintaining heat inside the bag is very important - use baffles and drawstrings correctly; mummy shaped bags works well.
the insular layer on the ground is critical in very cold temps. nothing beats a therma-rest or similar (note: a normal inflatable mattress does not work well since the air in he mattress gets freezing and does not insulate; thermarests etc has foam in the mattress that helps form an insular layer).
a friends wife made us fleece inners - bought 300-grade fleece; just stitched it together (no zipper) in a square box; cost like a 100bucks and adds between 5 and 10 degrees to a bags performance.

+1 on the liner. I also have a homemade one, cost less than R80. It's made of pretty much the same stuff that t-shirts are made of, adds heat, wicks moisture when it's hot, add allround comfort to a bag.

Biggest plus is that you have to wash your sleeping bag a LOT less often. Whether down or microfibre, washing adversly affects the insulating properties of sleeping bag fills.

You don't need all that stuff, any semi-decent bag will do. Sleep in your clothes, it doesn't tangle and if you are cold and have to zip two bags together for some extra heat, you don't have to trade your bag in for a pram.

Mr Sir HRH Moksie, have you actually slept in a wet down bag? And a wet synthetic one?

My man, Andy says:
INSULATION CARE
There is nothing as great as a bone dry down sleeping bag. Unfortunately there is also nothing as grim as a wet one. Saturated down loses 90% of its insulation as the delicate structure of the clusters stick together and collapse. The down absorbs a lot of water and because it loses most of its thermal performance it must be dried via an outside heat source like the sun, a tumble dryer or a body.

orraait orraait, seems i had the wet down the wrong way - recalled reading on one of the older versons of the first ascent websites that wet down has up to 60% of its normal insular ability. happy to agree that it is probably less.
so, down = light & comfy
synthetic = cheap & insulate when wet

Survival courses should tell you to:
1) add a cover for your head (beanie, buff), or
2) add socks for your feet
if you encounter extreme cold. Inner is great 'cept for the 'tangle' factor - if you can lie still, its a plus...
And don't underestimate what a good pillow can do! Try it.

BTW - have you ever tried to wash a down sleeping bag? It takes a lot of effort to get the down really wet. i.e. you need to force the bag under water AND squeeze the air out.

until it gets saturated, it is still very puffy and I'd imagine still really effective. I have slept in the dew a few times and the bag is still warm/good.

Thus, unless you submerge and hold your sleeping bag in a river, or sleep directly on the snow, I cant see it getting really wet in a hiking/trekking trip. I'd hazard a guess that even rain will not completely saturate a bag.

I found the following system works extremely well in cold conditions: use an inner thermal lining, as well as an "outer sleeping bag" (I think the common term now used is "bivvy bag"); and a beanie on one's pip.

I used this for temps around -12 degrees (possibly a bit colder), using a -8 degree down sleeping bag; with only a relatively light layer of clothing. The bivvy bag, in my opinion, was the key to my keeping nice and toasty, as it ensures that the heat generated within the sleeping bag isn't lost, or the cold from seeping into the sleeping bag. Almost everyone else (who just had inners) on the tented trip went to bed with almost their entire warm weather "wardrobe", including down jackets, and still froze!